1. Technical Field
This invention pertains to the class of devices for the collection and utilization of solar energy and, more particularly, to devices utilizing solar energy for interior lighting.
2. Related Art
Due to lack of space, in the design or renovations performed to a building many rooms or parts of houses, sheds, offices, storerooms, and the like, are left without much natural light. This situation causes the immediate need to resort to electrical lighting, with the consequent cost incurred due to electrical consumption.
Whenever possible, alternative lighting by means of skylights which are preferably placed on an already existing roof should be considered. Currently available skylights, however, show some deficiencies. One problem is that making a large opening in the roof where the skylight is going to be placed is invariably necessary. Making this hole is usually difficult and expensive, particularly when the roof is a reinforced concrete slab. The larger the hole, the more difficult and expensive this is.
A second problem with large holes is that of break-ins through the skylight. In order to avoid a break-in, these openings require, besides the sky-light itself, the installation of bars to impede the access to the interior, thus increasing the installation cost. This can also be an esthetic problem.
Another problem is that of rain leakage where the skylight meets the roof. The bigger the opening, the greater the risk of rain leakage. Yet another problem is that most of the existing skylights are not very decorative. Most of them do not correspond with the room's interior design criteria and are not easily adapted to do so.
A number of U.S. patents address aspects of solar energy collection. For example, the following U.S. patents describe devices for the concentration of solar energy generally for solar heating purposes but do not describe use for interior lighting. U.S. Pat. No. 3,899,672, to Levi-Setti, entitled Solar Energy Collection, U.S. Pat. No. 3,923,381 to Winston entitled Radiant Energy Collection, U.S. Pat. No. 4,003,638 to Winston, entitled Radiant Energy Collection and U.S. Pat. No. 4,131,485 to Meinel et al., entitled Solar Energy Collector and Concentrator all describe conical or trough-shaped solar collection devices for solar heating. Other patents describing the use of parabolic or curved mirrors to concentrate solar energy include U.S. Pat. No. 3,964,464 to Hockman, entitled Solar Radiation Collector and Concentrator, U.S. Pat. No. 4,222,370, to DeGeus, entitled Nontracking Concentrating Solar Collector, and U.S. Pat. No. 4,561,424, to Gill et al., entitled Nontracking Parabolic Solar Energy Collecting Apparatus. U.S. Pat. Nos. 3,902,794, to Abrams, entitled Fresnell Lens, and 4,612,913, to Mori, entitled Solar Energy Collector Array, use Fresnel reflectors for concentration. Other approaches are seen in U.S. Pat. Nos. 5,374,317, to Lamb et al., entitled Multiple Reflector Concentrator Solar Electrical Power System and 5,578,140, to Yogev et al., entitled Solar Energy Plant, describe multiple reflector systems. U.S. Pat. No. 5,062,899, to Kreuer, entitled Wide Acceptance Angle, High Concentration Ratio Optical Collector, describes a Cassegrain collection system. None of these patents, however, specifically describes a device designed to transmit the collected light to a room for lighting.
A number of patents do describe the collection of sunlight to provide room lighting. Some of these involve the use of transparent domes or skylights on the roof. Examples include U.S. Pat. No. 4,329,021, to Bennet et al., entitled Passive Solar Lighting System, U.S. Pat. No. 4,349,245, to Kliman, entitled Modular Natural Lighting System, U.S. Pat. No. 4,883,340, to Dominguez, entitled Solar Lighting Reflector Apparatus Having Slatted Mirrors And Improved Tracker, U.S. Pat. No. 5,099,622, to Sutton, entitled Skylight, U.S. Pat. No. 5,467,564 to DeKeyser et al., entitled Daylight Collection And Distribution System, U.S. Pat. No. 5,493,824 to Webster et al., entitled Rotatably Mounted Skylight Having Reflectors, U.S. Pat. No. 5,648,873, to Jaster et al., entitled Passive Solar Collector, and U.S. Pat. No. 5,655,339, to DeBlock et al., entitled Tubular Skylight With Improved Dome. However, in all of these patents, only the sunlight impinging on an area essentially equal to that of the skylight roof hole is transmitted. That is, there is no concentration and use of sunlight falling away from the aperture in the roof. Thus, to bring in reasonable amounts of sunlight may require quite large roof apertures.
A number of U.S. patents do describe interior lighting using means of collecting and concentrating sunlight from a wider area than the skylight access hole through the roof. For example, U.S. Pat. No. 4,201,197, to Dismer, entitled Solar Energy Collector Having A Fiber-Optic Cable, uses a parabaloidal mirror and a smaller mirror to focus light onto fiber-optics. This device involves a parabolic dish which must be motorized to track the sun, however. U.S. Pat. No. 4,306,769, to Martinet, entitled Interior Illumination Apparatus Using Sunlight, describes a trumpet-shaped light pipe with a secondary reflector. This apparatus, however, requires vertical support of the collection trumpet on top of the light pipe, probably increasing the weight and limiting the size of the trumpet collector. U.S. Pat. No. 4,411,490, to Daniel, entitled Apparatus for Collecting, Distributing and Utilizing Solar Radiation, involves a complex array of solar gathering cells, which are probably expensive and difficult to install. U.S. Pat. No. 4,475,536, to Dame, entitled Solar Collector-Skylight Assembly, describes a complex arrangement of parabolic reflectors. Its design is complex and undoubtedly expensive, resulting from its dual function as a solar heater. U.S. Pat. No. 4,514,414, to Mori, entitled Apparatus for Collecting Sunlight, describes a tall, roughly conical reflector. This system is actually designed to collect diffuse rather than direct sunlight, and the device has a fairly large mass compared to its light collection area, both factors probably limiting the amount of light usefully transmitted to the interior. U.S. Pat. No. 4,575,196, to Clegg, entitled Conical Beam Concentrator, is a device consisting of a vertical series of lenses. Such a device is undoubtedly expensive and may have weight limitations on its size. U.S. Pat. No. 5,540,216, to Rasmusson, entitled Apparatus And Method for Concentrating Radiant Energy Emanated By A Moving Energy Source, involves a static collector using two facing concave reflectors; the second reflector including small convex surfaces, which divert the beams towards an objective. The complexity of the surfaces of this device probably makes it expensive to manufacture. Thus the devices described in the above patents probably suffer from problems of expense, limited light transmission, or difficulty of installation.
Based on my observation of the art, I have discovered that what is needed is an improved skylight with a narrow light conduit penetrating the roof which nonetheless provides a high transmission of light from the outside to the inside of the building. Such a skylight, which concentrates sunlight but requires only a small aperture in the roof, can solve the problems addressed earlier, including minimizing the size of the hole which must be made to the roof, lowering the installation cost, avoiding the hazard of break-ins, and improving room esthetics.